Evaluation of Strain and Shear Effects in Pharmaceutical Blends Using near Infrared Spectroscopy

The objective of this study was to determine whether changes in strain and shear on pharmaceutical blends lubricated with magnesium stearate lead to changes in their near infrared (NIR) spectra. This study is important since a number of researchers have reported manufacturing problems associated with magnesium stearate lubrication. Near infrared spectroscopy does not require sample preparation, and is capable of obtaining spectra while a process occurs. Pharmaceutical manufacturing would be benefited by a method capable of monitoring a pharmaceutical process and indicating whether a blend is adequately lubricated. Near infrared spectra were obtained for pharmaceutical blends consisting of microcrystalline cellulose, lactose, and lubricated with magnesium stearate, but differing in terms of the strain and shear effects during lubrication. The lubricated blends were previously classified in terms of the number of revolutions applied during lubrication and the number of revolutions per minute. The NIR spectra were evaluated using the Pirouette (Infometrix, Bothell, WA) software for multivariate analysis. Principal component analysis for the region between 6260 cm^-1 and 5338 cm^-1 showed that samples from 1 rpm and 40 rpm show significant variation, while samples from the higher velocities such as 245 rpm show very little variation along the first principal component. These preliminary results indicate that NIR may be able to discriminate between samples that have undergone differences in lubrication.